I've just take a look on QCAD demo 2.2.1.0, and at a first glance I like it.

However, I have some questions about working with splines, which I was unable to answer with the documentation:

1.) How can I add/remove control points to/from existing splines?
2.) How can I modify the multiplicity of a control point? It is possible to move multiple control points to the same position, and the spline correctly "sharpens" at that position. But how can I move a single one of those multiple control points at a position to somewhere else, in order to get a smooth curve again?
3.) Is there any way to use splines as part of a poly line?
4.) What are the specific plans regarding splines support for future releases?

Spline support in QCad is very basic at this point. This is mainly because splines are rarely used in most areas of mechanical engineering, architecture or schematics design.

It is not possible to add control points, remove control points or modify their multiplicity. Adding multiple control points in one location to sharpen the spline is possible. You won't be able to separate them again later though.

It's a pity, since from a traffic engineering's point of view, irregular shapes are quite important. At least adding and removing control points should be a possible to make the splines feature usable. I cannot replace a whole spline every time I realize a control point is missing.